Food Science: Cotton Candy

It’s time again for the Eastern Idaho State Fair. And with it come those odd-ball foods that we don’t often see the rest of the year—stuff like deep-fried Snickers candy bars, maple bacon sundaes, tiger ears, and cotton candy.

In honor of the fair and its wacky foods, we thought we’d examine the history, science, and even a medical application associated with one of these strange treats: cotton candy. Cotton candy has been around for more than 100 years, but there’s still something magical about it.

History

Can you imagine your dentist promoting cotton candy, which is simply sugar mixed with food coloring and perhaps a bit of flavoring? Strange as it may seem, this would have been the case if you had lived at the turn of the 19th century and your dentist was William Morrison. In 1897, Morrison and a candy maker named John Wharton patented a device that made cotton candy. Calling it “fairy floss,” the partners took their new product to the 1904 World’s Fair and sold it for 25¢ a box—the equivalent of about $6 today. The partners grossed $17,163.75, which is more than $410,000 in today’s dollars (Historic Hudson Valley 2012).

Before Morrison and Wharton invented their machine, no one had come up with a way to induce the physical change necessary to transform sugar crystals into cotton candy. As early as the 1400s, however, Italian cooks were creating cotton candy’s culinary ancestor. Using what was then a new labor-intensive technique, these cooks melted sugar and used forks to separate it into fine strands called spun sugar to create various decorative forms that graced the tables of the European aristocracy. Because it was so rare at the time, sugar was kept under lock and key. And because of the high cost of sugar and the labor involved, this was a treat only the very wealthy could afford.

ay, automated machines and cheap sugar allow cotton candy to be produced in high quantities, packaged, and marketed to the masses.

Making Cotton Candy

The process of making cotton candy is direct example of an important process in physics called a phase change. The cotton candy process illustrates the phase change between physical states of matter (in this case, sugar) from a solid state to a liquid and then back to a solid again. A typical cotton candy machine includes a spinning head that contains the sugar (chemically known as sucrose) used to make the cotton candy. The walls of the head have a myriad of tiny holes, each of which is smaller than a grain of sugar. At the top of the head, a heater warms the sugar to 300F. As the sugar melts and the head spins at 3,400 revolutions per minute, things get interesting.

"At [the crystal] stage, the sugar molecules are organized very uniformly with neighboring molecules,” says Rich Hartel, a food scientist at the University of Wisconsin. “It’s like a parking lot filled with perfectly neat rows of the same car.” But once the sugar goes through a cotton candy machine, the crystals change form; the sucrose “parking lot” goes haywire.

That’s because heat breaks down the bonds of the sucrose crystals and splits each of them into their two component sugars, glucose and fructose. This process produces a sugary syrup. Meanwhile, something else is happening. According to Isaac Newton’s law of inertia, objects in motion tend to travel in a straight line at constant speed unless acted on by an external force. The spinning motion of the head, coupled with the inertia from the sugar pushes the liquid sugar through the small holes in the head and toward a large “catch” bowl surrounding it. This is the same principle used in a sling shot. These streams of sugar are so fine—about 50 micrometers (one millionth of a meter) in diameter—that they solidify immediately. “The rate [at which] something cools depends on its volume (space occupied by an object),” says Hartel. “The smaller the volume, the faster it cools.”

This quick cooling of the liquid as it shoots out of the holes in the head and into the open air allows no time for the sucrose molecules to re-group. Consequently, the strands aren’t sugar crystals; they’re actually thousands of strands of sugar glass, or sucrose molecules, that solidify without structure (The Free Library 2013). These hardened strands have many of the same characteristics as cotton fibers, which is how cotton candy got its name.

As sugary threads land in the catch bowl surrounding the head, the machine operator twirls a stick or a cone along the rim of the bowl to gather the candy into a poofy collection of air and sugar.

Because this treat consists of sugar, it’s tasty. However, consumed in large quantities, it is bad for you. Men’s Health magazine rates cotton candy No. 6 on its list of Six Terrifying Theme Park Foods (Men’s Health 2013). “Essentially, this treat is no different than eating sugar straight from the bag . . . ,” states an article on menshealth.com. “That’s enough to shift your body into fat-storage mode and land you a belly as soft as the confection you’re eating."

Medical Application

While consuming too much cotton candy has ill effects, two researchers may have found a good use for it.

They’re attempting to use cotton candy to create networks of blood vessels in laboratory-grown bone, skin, and muscle. Dr. Jason Spector of New York Presbyterian Hospital/Weill Cornell Medical Center in New York and Leon Bellan of Cornell University have teamed up to develop the idea.

According to an article in the Denver Post, the technique would work like this (Ritter 2009): “First, you pour a thick liquid chemical [i.e., an epoxy material] over a wad of cotton candy. Let the liquid solidify into a chunk and put that in warm water to dissolve the candy. That leaves tiny channels where the strands of candy used to be. So you have a chunk of material with a network of fine channels within.

“Next, line these channels with cells to create artificial blood vessels. And seed the solid chunk with immature cells of whatever tissue you’re trying to make. The block is biodegradable, and as it disappears, it will gradually be replaced by growing tissue. In the end, you get a piece of tissue permeated with tiny blood vessels.”

This research is still in the early stages, but the technology has the potential to allow scientists to engineer much thicker tissue than ever before.

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